Ranavirus-associated mass mortality in imported red tailed knobby newts (Tylototriton kweichowensis): a case report

A mass die-off of imported red tailed knobby newts (Tylototriton kweichowensis) occurred in 2004 in Belgium and the Netherlands. In addition to massive infection with Rhabdias tokyoensis, Ranavirus was isolated from three dead newts examined virologically and the gene coding for the major capsid protein of the virus was sequenced. The isolate showed 99.8% similarity to the published sequence of frog virus 3. Upon experimental infection of axolotls (Ambystoma mexicanum) with this isolate, no marked pathology was noticed and the virus could not be re-isolated at 9weeks post-inoculation. Apart from the possibility of exposure of a non-sensitive host, the mortality episode in the newts may be related to stress resulting from the importation of the newts in breeding condition. This possibility is supported by the presence of degenerating egg-follicles in the females.